﻿// RankingSejmowy 1.0 - Polish parliment statistics for the masses.
// Copyright (C) 2010 Jarosław Dubrownik
//  
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//  
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//  
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
namespace RankingSejmowy.Model
{
    public class Entity<T>
    {
        private int? _hashCode;

        public virtual T Id { get; set; }

        public override bool Equals(object obj)
        {
            var other = obj as Entity<T>;
            if (obj == null)
            {
                return false;
            }

            var def = default(T);
            var otherIsTransient = Equals(other.Id, def);
            var thisIsTransient = Equals(Id, def);
            if (otherIsTransient && thisIsTransient)
            {
                return ReferenceEquals(other, this);
            }

            return other.Id.Equals(Id);
        }

        public override int GetHashCode()
        {
            if (_hashCode.HasValue)
            {
                return _hashCode.Value;
            }

            var thisIsTransient = Equals(Id, default(T));
            if (thisIsTransient)
            {
                _hashCode = base.GetHashCode();
                return _hashCode.Value;
            }

            return Id.GetHashCode();
        }
    }
}